n] OF ANTHOCYANINS 21 



in the shade is a peculiar function of the lamina, and is not connected 

 with general reddening of the plant. 



In petioles, anthocyanin is more frequent than in leaves, and in 

 stems one might say that it is almost universal; the stem may be 

 entirely red, or only red at the basal internodes : or the nodes may be 

 red and the internodes green, or vice versa. A spotted effect produced 

 by the local distribution of anthocyanin is seen in some stems, for 

 example in Chaerophyllum temulum and Conium maculatum (Umbelli- 

 ferae). 



Red pigment is also very characteristic of the bud-scales of trees 

 and shrubs; in some cases these scales represent leaf-bases (Aesculus 

 Hippocastanum, Acer pseudoplatanus, A. campestris}., in other cases, 

 stipules (Ulmus campestris, Tilia europaea). In addition the stipules 

 of herbaceous plants are often red, and the same statement holds good 

 for enlarged leaf -bases (Umbelliferae). 



2. Anthocyanin is characteristic, though by no means universally 

 so, of young developing leaves and shoots. It is interesting to note 

 how in some species one finds both reddening of young leaves and 

 autumnal colouring, whereas in others this is not the case. There 

 are, in fact, four possibilities: 



(a) Both anthocyanin in young leaves and autumnal reddening. 

 Species of Acer, Rosa, Crataegus and Rubus. 



(6) Anthocyanin in young leaves but no autumnal reddening. 

 Corylus Avellana, Juglans regia, Fraxinus excelsior and Quercus Robur. 



(c) No anthocyanin in young leaves but some autumnal reddening. 

 Aesculus Hippocastanum. This is a much rarer combination than (a) 

 or (fe). 



(d) No anthocyanin in either young or old leaves. Fagus sylvatica 1 . 

 Anthocyanin is especially abundant in the leaves of certain tropical 



trees (Cinnamomum, Haematoxylon, etc.) ; in addition to being coloured 

 red, the young leaves often hang vertically downwards and straighten 

 up again when mature (Bauhinia, Dryobalanops, Cinnamomum) 2 . 

 In other species, especially among the Caesalpineae group of the 

 Leguminosae, the whole young shoot has a vertical position, and in 

 this respect, together with its intense red colour, forms a striking 

 contrast to the older parts of the tree with green leaves in the normal 

 horizontal position. As instances, certain species are mentioned by 

 Stahl (405) and Keeble (403) : Amherstia nobilis with young leaves of 



1 Pick (391) reports the presence of anthocyanin in young Beech leaves. 

 Willis, J. C., The Flowering Plants and Ferns t Cambridge, 1904, p. 157 



